我是springboot的新手，尝试实现我从这个链接中学到的东西：登录注册特性。我的目标是建立一个用户登录和注册功能，但我遇到了这个错误：

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APPLICATION FAILED TO START

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Description:

Field authenticationManager in com.x.assignment.auth.service.SecurityServiceImpl required a bean of type 'org.springframework.security.authentication.AuthenticationManager' that could not be found.

The injection point has the following annotations:
    - @org.springframework.beans.factory.annotation.Autowired(required=true)

Action:

Consider defining a bean of type 'org.springframework.security.authentication.AuthenticationManager' in your configuration.

我的文件夹结构，代码与链接中提到的相同。但不明白为什么@autowired不起作用。请帮帮我。谢谢您。